Data will be collected by analysis of the EM autoradiograms to determine whether cycloheximide has an inhibitory effect on the amino acid incorporation into proteins by presynaptic endings in vitro. EM autoradiograms of synaptosomal fractions from cerebral cortex of rats injected with H3 uridine will be analyzed to determine whether the presynaptic endings contain RNA. It will be attempted to determine whether the intraaxonal H3 present in the rabbit optic nerve after intraocular injection of H3 uridine is a product of local synthesis or comes from the ganglion cells of the retina through axonal flow. The electron microphotographs obtained from the superficial neuronal rows of the lamina pyramidalis of the sensori-motor cortex of malnourished and control rats will be analyzed for determining size and density of presynaptic endings and size and density of neurons and glial cells. The effect of actinomycin D on the myelin will be studied further using other RNA and protein synthesis inhibitors in the attempt to determine whether the splitting at the level of the intraperiod line produced by this drug is secondary to the protein synthesis inhibition or due to a nonspecific toxic effect.